r语言中的循环_R语言中的循环

向右看齐 2023-03-05 06:29 42阅读 0赞

r语言中的循环

Sometimes the programmers need to encounter a situation where they need to execute a particular block of code many times. Everyone is acquainted with the fact that usually whenever there is a block of code then the statements in them are executed sequentially. However, if a situation exists where the user needs to run the same block multiple times then it will be difficult to write the same code for those many times as needed. Therefore keeping the advancing requirements and needs of the users in the programming world certain functions are inbuilt in any programming language to ensure the comfortable atmosphere around the programmers. The above-stated functions are nothing but so-called loops in any programming language.

有时，程序员需要遇到需要多次执行特定代码块的情况。 每个人都熟悉这样一个事实，通常只要有代码块，它们中的语句便会顺序执行。 但是，如果存在用户需要多次运行同一块代码的情况，那么将难以根据需要多次编写相同的代码。 因此，为了满足编程世界中用户的不断提高的需求和要求，某些功能内置于任何编程语言中，以确保程序员周围的舒适氛围。 上述功能不过是任何编程语言中的所谓循环。

## 循环 **(**Loops**)** ##

Coming to the brief description of **loops**, **loops** are inbuilt functions that run the same block of code repeatedly. Commonly a **loop statement** allows the users to execute a statement or a block of statements multiple times. In loops, we generally follow a particular format in which there are several parameters like conditional along with conditional code when the conditions inserted become either true or false. The following is the general chart of the above-mentioned parameters. Coming to the brief description of loops, loops are inbuilt functions that run the same block of code repeatedly. Commonly a loop statement allows the users to execute a statement or a block of statements multiple times. In loops, we generally follow a particular format in which there are several parameters like conditional along with conditional code when the conditions inserted become either true or false. The following is the general chart of the above-mentioned parameters.

简要介绍一下**循环** ， **循环**是内置函数，可重复运行相同的代码块。 通常， **循环语句**允许用户多次执行一条语句或一段语句。 在循环中，我们通常遵循一种特殊的格式，其中当插入的条件变为true或false时，会有多个参数(例如conditional)以及条件代码。 以下是上述参数的一般图表。 简要介绍一下循环，循环是内置函数，可重复运行相同的代码块。 通常，循环语句使用户可以多次执行一条语句或一段语句。 在循环中，我们通常遵循一种特殊的格式，其中当插入的条件变为true或false时，会有多个参数(例如conditional)以及条件代码。 以下是上述参数的一般图表。

The users working with the R will get a chance to acknowledge the **different types of loops** and **loop statements**.

使用R的用户将有机会认识到**不同类型的循环**和**循环语句** 。

There are mainly three types of loops. They are:

循环主要有三种类型。 他们是：

1.  repeat Loop
    
    重复循环
2.  while Loop
    
    while循环
3.  for Loop
    
    循环

### 1.重复循环 **(**1. repeat Loop**)** ###

Using the **repeat loop statement** a particular group of statements can be executed repeatedly. And, on the other hand, it also shortens the code written.

使用**重复循环语句** ，可以重复执行特定的一组语句。 并且，另一方面，它也缩短了编写的代码。

**Syntax:**

**句法：**

repeat {   
           //code to be executed   
           if(exit_condition) {  
              break  
           }  
        }

Initially, we ought to initialize some variables which are taken by the **repeat loop** and thus are processed. Along with the initialization variables, one should also declare a condition in the **repeat loop**. This specific condition is checked and later the group of statements is executed as per the boolean obtained after checking the condition. Finally, the **repeat loop** uses a *break* statement for coming out of the **repeat loop**.

最初，我们应该初始化一些由**重复循环获取**并因此被处理的变量。 除初始化变量外，还应在**重复循环中**声明一个条件。 检查此特定条件，然后按照检查条件后获得的布尔值执行语句组。 最后， **重复循环**使用*break*语句从**重复循环中出来** 。

Have a look at the following example which depicts the usage of the **repeat loop in the R language**.

请看以下示例，该示例描述**了R语言中重复循环**的用法。

**Example:**

**例：**

# Initialising the counter and then 
    # using it in the repeat loop
    i <- 1 
    repeat {
         
      print("Welcome to includehelp.com") 
      i <- i+1     
      if(i >= 4) {
         
         break 
      } 
    }

**Output**

**输出量**

[1] "Welcome to includehelp.com"
    [1] "Welcome to includehelp.com"
    [1] "Welcome to includehelp.com"

### 2. while循环 **(**2. while Loop**)** ###

In the **while loop**, the block of statements will be repeatedly executed till the *entry\_condition* is *true*. But prior to that, the *while* condition is checked and it must turn.

在**while循环中** ，语句块将重复执行，直到*entry\_condition*为*true* 。 但在此之前，将检查*while*条件，并且必须转为条件。

**Syntax:**

**句法：**

while (entry_condition) {  
           //Code to be executed  
        }

In general, a **while Loop** is called an "**entry controlled loop"** in programming languages. This is because prior to the execution of the block of statements the **while loop** initially checks for the trueness in the condition and then if the condition becomes *true* the statements are executed sequentially.

通常， **while循环**在编程语言中称为“ **入口控制循环”** 。 这是因为在执行语句块之前， **while循环**首先检查条件中的真实性，然后如果条件变为*true* ，则按顺序执行语句。

**Example:**

**例：**

i <- 1
    while (i <= 10) {
        
     print(i*i)
     i = i+1
    }

**Output**

**输出量**

[1] 1
    [1] 4
    [1] 9
    [1] 16
    [1] 25
    [1] 36
    [1] 49
    [1] 64
    [1] 81
    [1] 100

### 3. for循环 **(**3. for Loop**)** ###

The main purpose of the **for loop** is the same as the **while loop**, it checks the condition prior to before executing the group of statements. On the other hand, we also have loop control statements along with the different types of loop statements.

**for循环**的主要目的与**while循环**相同，它在执行语句组之前先检查条件。 另一方面，我们还具有循环控制语句以及不同类型的循环语句。

**Syntax:**

**句法：**

for (valuetoIterate) {  
            //code to be executed 
        }

Here the above syntax helps the users in making use of the **for loop** in R. To support the flow of the while loop now let us consider an example and apply the above concept to it.

在这里，上面的语法帮助用户使用R中的**for循环** 。现在，为了支持while循环的流程，让我们考虑一个示例并将上述概念应用于该示例。

**Example:**

**例：**

A<- c(432, 35, 45, 14)
    
    print("Values of the vector:")
    for ( i in A){
          
      print(i) 
    }

**Output**

**输出量**

[1] "Values of the vector:"
    [1] 432
    [1] 35
    [1] 45
    [1] 14

> 翻译自: [https://www.includehelp.com/r/loops.aspx][https_www.includehelp.com_r_loops.aspx]

r语言中的循环

[https_www.includehelp.com_r_loops.aspx]: https://www.includehelp.com/r/loops.aspx